Channing Tatum met his producing partner, Reid Carolin, on the set of Kimberly Peirce’s 2008 Iraq war drama Stop-Loss. A decade later, they’ve fittingly returned to the battlefield for their new HBO documentary War Dog: A Soldier’s Best Friend.

Directed by Deborah Scranton, War Dog highlights the intimate relationship between U.S. Special Operations soldiers and the K9s that serve alongside them in combat. We spend time with dogs Layka, Mika, and Pepper, who serve with their handlers on the front lines — where communication travels up and down the leash in a nameless language, and where the two-legged and four-legged warriors are considered equal members of a team. The film is alternately heartwarming and heartbreaking as it traces the relationships between these dogs and their owners, many of whom struggle with grief or PTSD.

Tatum and Carolin were brought into the project by Brett Rodriguez, a producer who had just returned from Iraq. (“I have a friend named John who is trying to get his dog back,” the pair recall Rodriguez saying to them.) As creatives interested in amplifying veterans’ stories, signing on was a no-brainer for Carolin and Tatum — especially since they have a soft spot for man’s best friend. “Channing and I are both dog lovers,” Carolin gushes. “Our dogs go everywhere with us.”

The tiny percentage of military K9s who are chosen for special operations are treated like soldiers, and as such, they develop a special kind of bond with the humans who work with them. “They start to have personalities that are as complex as you or I,” Carolin says. “The line between dogs and humans is very thin.” In the film, we see dogs helping their owners through struggles with grief and addiction, falling in love with TV shows like Grey’s Anatomy, and fighting like honest-to-goodness soldiers on the battlefield. Tatum says he learned on the project that there’s a tendency to treat soldiers — human or canine — like “tools,” as if they’re “machines that just do a job.” He adds of military K9s, “They’re not just a weapon — they’re a living thing.”

Indeed, as much as the film is an ode to the wondrous relationships that can form between dogs and humans, it’s often an unsettlingly — even surprisingly — intimate portrait of soldiers and veterans. The presence of the dogs, in a way, provides an accessible entry point into a more challenging film. “The [veterans] opened up [to us],” Carolin explains. “They’re highly skeptical of the media, I think rightly …. We’re really proud of the fact that they felt safe enough to be vulnerable in front of a camera for us.” Those featured in War Dog discuss what motivated them to join the military, disclose their traumas and fears, and explain at length the essential relationships they’ve formed with K9s.

HBO

War Dog is a heavy, affecting watch, and yet through its steadfastly emotional focus on relationships and experiences, it transcends the divisiveness of the current political climate. “Because it’s a volunteer army, there’s a huge divide between the military and the rest of the country,” Carolin says. “[The documentary] allows people to connect to these soldiers without there being a political filter.” Tatum agrees, arguing that anyone can get behind the patriotism demonstrated by a military dog: “These dogs just show up. They don’t know about politics. They don’t know the Bible or the Quran. They just know to fight for their team.”

While working on the film, Tatum and Carolin briefly went to Afghanistan — which Tatum calls “an experience in itself” — but were mostly “cheerleaders” for Scranton, Rodriguez, and the rest of the team. It’s the latest example of the pair, who’d previously backed Tatum vehicles 22 Jump Street and Magic Mike XXL, going more indie as producers. Their other 2017 titles are Logan Lucky, Steven Soderbergh’s gonzo comeback movie, and Comrade Detective, the Amazon spoof series that evolved out of a call for “the worst idea” that they could think of. Tatum says there’s no science to the shift, and describes their producing approach thusly: “We sprint wholeheartedly” — even if the ideas turn out to be flat-out terrible.

Compared to Comrade Detective, War Dog “is a way less outside-the-box idea,” Tatum continues. “Nevertheless, it’s still diving into something that may be uncomfortable to watch — and there’s truth in that.” It’s why the film’s lack of political slant, Carolin argues, is so important — to create room for empathy, for understanding, and for finding some common ground. That it happens to be about dogs best explains why anyone who watches can connect to it. “Dogs are a unifying force — they are inherently apolitical,” he says. “We empathize with them because they represent the best parts of who we are.”

War Dog: A Soldier’s Best Friend launches Saturday morning on HBO Go and HBO Now, before making its television premiere Monday at 8 p.m. ET.